Firefox does not trust a particular secure website that I know is secure but it does trust other secure websites

Firefox does not trust a specific secure website that I know is secure, but it does trust other secure websites. Also, Internet Explorer trusts this website and Firefox on another computer trusts this same website. When I try to connect Firefox tells me that it does not have a valid certificate (even though I know one exists) and that I would have to make an exception to connect. Is there some way I can correct this and get the proper certificate into this particular Firefox program?

Firefox does not trust a specific secure website that I know is secure, but it does trust other secure websites. Also, Internet Explorer trusts this website and Firefox on another computer trusts this same website. When I try to connect Firefox tells me that it does not have a valid certificate (even though I know one exists) and that I would have to make an exception to connect. Is there some way I can correct this and get the proper certificate into this particular Firefox program?

Chosen solution

Make sure to select the "All Files" type and not "Text files" when you save the file in Notepad (Text files will append a hidden .txt file extension).

It is possible that the server doesn't send a required intermediate certificate.
Firefox stores intermediate certificates that servers send for future use, so if you have visited a website that has send such a certificate then you won't see an error if you visit a server that doesn't send that intermediate certificate.

Click the "View..." button and inspect the certificate and check who is the issuer.

You can see more Details like intermediate certificates that are used in the Details pane.

Can you post a link to that website?
It is possible that the server doesn't send a required intermediate certificate.
Firefox stores intermediate certificates that servers send for future use, so if you have visited a website that has send such a certificate then you won't see an error if you visit a server that doesn't send that intermediate certificate.
You can inspect the certificate chain via a site like this:
*http://www.networking4all.com/en/support/tools/site+check/
You can retrieve the certificate and check details like who issued certificates and expiration dates of certificates.
*Click the link at the bottom of the error page: "I Understand the Risks"
Let Firefox retrieve the certificate: "Add Exception" -> "Get Certificate".
*Click the "View..." button and inspect the certificate and check who is the issuer.
You can see more Details like intermediate certificates that are used in the Details pane.

You can Copy and Paste the certificate text of the intermediate certificate to a .cer text file and import the certificate in the Certificate Manager or via Firefox > New Tab > Open File.

DO NOT set any trust bits, those are only required for root certificates and should never be set for intermediate certificates.

The www.canadadrugs.com server doesn't send a required intermediate certificate.
You can inspect the certificate chain via a site like this:
*http://www.networking4all.com/en/support/tools/site+check/
You can install (import) the second certificate (Secondary EV SSL Intermediate CA Certificate) from this VeriSign website.
*https://knowledge.verisign.com/support/ssl-certificates-support/index?page=content&id=AR1728
You can Copy and Paste the certificate text of the intermediate certificate to a .cer text file and import the certificate in the Certificate Manager or via Firefox > New Tab > Open File.
DO NOT set any trust bits, those are only required for root certificates and should never be set for intermediate certificates.